High-speed image processing is required to operate high-speed robots in a factory automation (FA) system or the like. For example, when a robot is configured with a feedback loop between its vision sensor and its actuator, the actuator can be controlled in units of milliseconds. Accordingly, the image processing speed that matches this speed is required. However, because the image processing speed in modern vision systems is limited by the video frame rate, the robot can only operate at low speeds that match this image processing speed. It is impossible to take full advantage of the robot's performance.
There are some high-speed CCD cameras that can take images at intervals of about one (1) millisecond. In these devices, the images are temporarily stored in memory and later read and processed. Therefore, the devices can be applied to such applications as image analysis. However, the devices have almost no real-time capability, and are not suitable for controlling robots or similar real-time applications.
In order to overcome these problems, institutes such as the Massachusetts Institute of Technology, the California Institute of Technology, and Mitsubishi Electric Corporation have been researching a vision chip that combines the image reading portion and the processing portion into one unit (“An Object Position and Orientation IC with Embedded Imager,” David L. Standley, Solid State Circuits, Vol. 26, No. 12, December 1991, pp. 1853–1859, IEEE); “Computing Motion Using Analog and Binary Resistive Networks,” James Hutchinson, et al., Computer, Vol. 21, March 1988, pp. 52–64, IEEE); and “Artificial Retinas—fast versatile image processors,” Kazuo Kyuma, et al., Nature, Vol. 372, Nov. 10, 1994). However, these chips employ a fixed analog circuit that is easy to integrate. Accordingly, these circuits have various shortcomings. That is, the circuits require subsequent-processing of output signals. The type of image processing they can perform is limited to special applications. The circuits have a lack of universality.
Japanese Unexamined Patent Application Publication No. HEI-10-145680 has proposed a vision chip that is capable of performing universal image processing. This vision chip is provided with a processing element for each photodetector. An analog-to-digital converter is provided for each photodetector row. The vision chip can reduce the processing time through parallel processing. The vision chip can also reduce the number of transmission lines between the photodetectors and the processing elements, achieving an optimal integration level for both.
It is noted that the center of gravity (first order moment) of an image is information that is required in many image processings. In order to calculate the center of gravity of an image, it is necessary to perform calculation onto image data of each pixel and positional information (x direction positional information and y direction positional information) of the subject pixel. It is therefore necessary to store, in advance, positional information of each pixel in a memory. When using the technology in the Japanese Unexamined Patent Application Publication No. HEI-10-145680, it is necessary to transfer, in advance, positional information of respective pixels from a control circuit to the corresponding processing elements in succession. Each processing element performs calculation onto image data that is received from a corresponding photodetector and its positional data, and outputs the calculated result. It requires a lot of time to transfer the positional information to the processing elements. It is desirable to enhance the speed of such a basic image processing operation.